Cut the ends off the ciabatta and slice horizontally. Cut each slab into 4 pieces. Brush the cut side with 2 tablespoons of olive oil and run under the broiler or grill to brown and crisp a bit. Keep warm. In a non-stick pan over medium heat, sauté the celery and garlic in the remaining 2 tablespoons of olive oil. Fry until the garlic just begins to colour. Turn the heat up a bit and add the mushrooms. Season with salt and pepper and fry until the mushrooms are tender and a bit browned around the edges.

Add the shrimp and parsley and cook, stirring, until the shrimp turn pink and curl. Spoon the mixture over the ciabatta and serve immediately. Serves 8 as a starter.